There are two things I know which cannot possibly be false and cannot possibly be proven:

- Knowledge exists
- So does ignorance

I suppose everything else comes from there. But here, as with everything else, I'm just guessing.

As a side note, if I were you I wouldn't be swayed by Harv's argument. "Thought happens" is just as fuzzy as "I exist". Your first, 100% sure statement cannot possibly be clear as words always beg definition. Perhaps you could write your fundamental statement as "___ ______". That would be tough to disprove!